Wideband SIW-Based Low-Cost Multilayer Slot Antenna Array for E-Band Applications

This paper proposes a substrate integrated waveguide (SIW) slot antenna array for the wideband gigabyte mobile radio application in the E-band. The wideband unit cell design is based on simultaneous feeding of four-element radiation slots with a higher order cavity mode directly excited by a simple slot aperture fed by a microstrip fork-like tuning stub. Employing the higher order mode along with the slot aperture facilitates low loss, simple feeding network, and lower sensitivity to fabrication errors. To cancel the beam tilt versus frequency, the higher-order-mode unit cell is used in a 2 x 2 array along with a differential feeding structure. The array was designed and taped out using a new high-resolution multilayer printed circuit board (PCB) technology and characterized by using the constructed millimeter-wave (mm-wave) measurement setup at KU Leuven/imec. This technology provides the possibility to stack microvias in PCBs and reduces the fabrication cost compared to other multilayer technologies in mm-wave bands. The proposed array in 2 x 2 array configuration has a measured bandwidth of 11.4 GHz (16%), a total efficiency of 69%, a realized gain of 12 dBi at 72 GHz, and a 3-dB gain bandwidth that covers the entire impedance bandwidth. In comparison with existing E-band SIW slot arrays (compensating for array sizes), the proposed design achieves similar or better performance in bandwidth but with lower cost, lower sensitivity to fabrication tolerances, and higher total efficiency.